Previously, robotic arms for vending machine applications and the like did not provide a mechanism to allow robotic arm members to move independently from the motor driving the arm member. The movement of arm members of prior art are permanently coupled to their respective driving motors. Therefore, if the movement of the arm member halts due to a collision or jam, or is abruptly reversed, damage to drivetrain components or the motor providing power to the arm is possible. Manual movement of the robotic arm members may also damage the drivetrain components or the motor.
Personal safety is also a concern because there is no mechanism to disengage the movement of the robotic arm member from the motor, and the motor will continue to drive the motion of the robotic arm member while power is provided to the motor.
Furthermore, previous robotic arms utilize non-absolute position encoders to provide position feedback to the vending machine control. The vending machine controller monitors robotic arm position by keeping count of encoder pulses. If any encoder pulses are lost, due to electrical noise, for instance, the position accuracy of the arm is reduced.